This invention relates to a device for regulating asynchronous rotating machines, especially motors and induction generators.
In some electrotechnical applications, motors are supplied with a fixed voltage and from a variable-frequency converter.
In this case, since the voltage remains constant, desaturation of the motor is obtained when the frequency increases, thus producing a reduction in torque.
In many applications, however, it is a desirable objective on the contrary to ensure that the torque developed by the motor increases with the frequency or at least remains constant.
One of the solutions at present adopted for the achievements of this objective consists in carrying out high-frequency chopping of the direct-current signal of the motor supply voltage by means of an electronic device and in remodulating the chopped wave, thus producing a new signal in order to obtain a ratio U (voltage)/F (frequency) which is substantially constant as a function of the speed of rotation of the motor.
However, these electronic devices suffer from the disadvantage of being very complex and therefore costly as well as producing noises and vibrations of the motor at low frequency.